1. The Field of the Related Art
The present invention relates to an optical fiber wiring apparatus for interconnecting optical switches, optical combiners, wavelength converters and other optical elements by optical fibers to configure a high-performance optical system.
2. Background of the Prior Art
The previous efforts made for lightwave transmission on fibers have been directed to its introduction into intercity or interoffice trunks. Currently, studies are being conducted to further extend the application of fiberguide transmission to subscriber loops. Unlike repeated transmission from one point to another on intercity or interoffice trunks, the transmission in subscriber loops requires that users distributed in a plane be provided with a communications network of high serviceability and efficiency that allows for quick recovery from failures, that is capable of fast response to regional variations in demand, and that has a high capacity factor. In order to configure such a flexible network, it is important to develop an optical crossconnect and a remote optical switch unit that carries optical signals and is capable of changing paths or lines. Previously, it has been difficult to realize a system that is small in size and is capable of multiple inputs and producing multiple outputs. The only product available today is an experimental version capable of eight inputs and eight outputs. One way the problem has previously been solved is to interconnect, in parallel multiple stages, a plurality of optical switches. The optical elements generally used for this purpose are not limited to optical switches alone. Optical combiners, wavelength converters, light sources, etc. are also connected in multiple stages to realize an optical crossconnect or switches of high performance. This is also the case for optical computers.
There are two approaches for interconnecting optical elements in multiple stages. One approach involves the use of optical wave-guides and the other uses optical fibers.
Optical wave-guides suffer significant insertion and transmission losses and no reliable technique for mounting optical elements on substrates has been established. Further, optical elements on substrates has been making thin substrates suitable for optical wave-guides and packing optical elements at high density is not as easy as in electrical substrates.
The second approach uses two basic methods. One is to connect the end of an optical element directly to the end of another optical element and the other is to wire optical elements with optical fibers fixed on a substrate as in the case of wiring electric circuits. These methods have a problem of increased equipment size, but compared to the first approach, are more practical since splicing and other connecting techniques are known. However, these two methods have had the following problems. In the first method, which connects the end of one optical element directly to the end of another element, optical fibers become cluttered as the number of interconnected elements increases. This cluttering causes either a significant drop in the efficiency of wiring operations or an increase in the number of wiring errors. Further, unfixed optical fibers will bend sharply at crossovers, leading to increased losses or lower strength. The problems of fiber cluttering and bending can be avoided in the second method, which wires optical elements with optical fibers fixed on the substrate. However, if a plurality of substrates are used to avoid crossing of optical fibers, interconnecting the substrates is not easy, compared with wiring electric circuits.